Re: markings on Screw Pitch Gauge?

> I've got an old screw pitch gauge that I inherited. There's no mfr's

> > name marked on it, just "Number 137". > > > the individual leaves are marked with two numbers each, but these > > numbers are not reciprocals. The first number is always a small > > integer which I presume is threads-per-inch. > > > the second number is always a decimal. > > > Any idea what the second set of numbers are? > > pairs of numbers are > ~~~~~~~~~~~~~~~~~~~~ > 60 - 0.021 > 48 - 0.026 > 40 - 0.032 > 32 - 0.040 > 30 - 0.043 > 28 - 0.046 > 26 - 0.049 > 25 - 0.051 > 24 - 0.063 > 22 - 0.058 > 20 - 0.064 > 19 - 0.067 > 16 - 0.080 > 14 - 0.091 > 13 - 0.098 > 12 - 0.107 > 11 - 0.115 > 10 - 0.126 > 9 - 0.142 > 8 - 0.160 > 7 - 0.183 > 6 - 0.215 > 5 - 0.259 > 4-1/2 - 0.284 (sic) > 4 - 0.320 > > looking at the leaves, "depth of thread" in inches seems the most > plausible to me. This item would date back to the 50's, I don't > believe there was too much metric action in American machine shops at > that time. > > I'd try _measuring_ the depths with a micrometer, but I don't know > where to measure to/from. How is thread depth defined? And by the > way, who sets the standards on how these things are measured?
Reply to
Jim Pugh
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treat the first number as TPI I have added witworth form thread depth in inches..... doubleing it gives the second number.

N.B. unified thread depth is diferent, at 40 tpi for exampe it's 0.015336.

Hope this helps

-- Jonathan

Barnes's theorem; for every foolproof device there is a fool greater than the proof.

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Reply to
Jonathan Barnes

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